Current investigation of pharmacologic methods to control massive periretinal proliferation (MPP) and its intravitreal counterpart, proliferative vitreoretinopathy (PVR) rely primarily on clinical observations such as the number of retinal detachments or the degree of severity of strand formation to judge the efficacy of treatment. There is no quantitative method for assessing the strength of fibrocellular vitreous strands and the resulting retinal traction. In this study we propose to use a newly-developed technique, vitreous microtensiometry (VMT) to measure in situ the physical properties of vitreous proliferations and assess quantitatively the effect of different treatments on the strength of vitreous strands and the traction of preretinal membranes. VMT combines in situ capillary viscometry with simultaneous photography through the operating microscope to obtain the local vitreous viscosity and measure the strength and extensibility of vitreous strands. Using the New Zealand White rabbit as our animal model, we propose to induce PVR by intravitreal injection of tissue-cultured fibroblasts. The animals will then be treated with the most promising cytotoxic drugs (5-fluorouracil, daunorubicin) and anti-collagen agents (beta-aminopropionitrile, d-penicillamine, cis-hydroxyproline). They will be sacrificed at regular intervals and the physical properties of their vitreous measured by VMT in order to assess the effect of the treatment on the severity and strength of the proliferative intravitreal strands. The results of these measurements, in conjunction with standard clinical evaluations, are expected to play an important role in developing optimal treatment regimens. We also propose to quantitate the ease of bacterial collagenase in facilitating vitrectomy by determining in situ tensile strength of intravitreal cicatricial tissue before and after enzyme treatment.